<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    body {margin: 0;overflow: hidden;}
    #canvas {background-color: antiquewhite;}
  </style>
</head>
<body>
  <canvas id="canvas"></canvas>
  <script>
    /** @type {HTMLCanvasElement} */
    const canvas = document.querySelector('#canvas');
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    const ctx = canvas.getContext('2d');

    ctx.lineWidth = 40;
    ctx.beginPath();
    ctx.arc(300,200,100,0,Math.PI * 2);
    ctx.fillStyle = 'rgba(255,0,0,0.5)';
    ctx.fill();

    ctx.lineWidth = 40;
    ctx.beginPath();
    ctx.arc(300,300,100,0,Math.PI * 2);
    ctx.fillStyle = 'rgba(255,0,0,0.5)';
    ctx.fill();

  </script>
</body>
</html>